Placing an implant: the steps, and what guided surgery adds

First: 3D imaging with cone beam CT

A cone beam CT is a dental scanner that produces a three-dimensional image of the bone. It shows the available height and width, the position of the nerve in the lower jaw and that of the maxillary sinus. A review of recommendations considers it justified for implant diagnosis and planning, provided the field of view and dose are adapted to each case: depending on the machine, the dose ranges from the equivalent of 2 to 200 panoramic radiographs ^[1]. Metal objects (crowns, implants) and patient movement can create artefacts that degrade the image ^[1].

This scan goes together with an assessment of the gums and neighbouring teeth. If periodontitis is present, it is treated and re-evaluated before any placement: an implant placed in an infected mouth starts at a disadvantage.

Where should the implant go? The decision starts from the tooth to be replaced

An implant’s position is not chosen where bone is most plentiful, but where the future crown needs to be in order to chew properly and be cleaned easily. On the computer, Dr Hazout therefore designs the tooth to be replaced first, then checks that the bone can hold an implant beneath it, at a safe distance from the nerve, the sinus and the neighbouring roots. If bone is lacking at that spot, a bone graft is discussed, rather than moving the implant to a less favourable position.

The surgical guide

The surgical guide is a splint, usually 3D-printed in resin, that sits on the teeth or gum. Its sleeves direct the drills along the axis decided on the computer. Guidance is called fully guided when all drilling and the implant insertion go through the guide, and partially guided when only the first drill is guided.

A guide is most useful when the margin for error is small: an implant close to the nerve or sinus, a narrow ridge, several implants whose axes must be parallel, or placement through the gum without lifting it. For a single tooth in wide bone, well-prepared freehand placement remains a common option.

Guided or freehand surgery: how accurate?

A meta-analysis of 20 clinical studies (2,238 implants) measured, with a static guide, a mean deviation of 1.2 mm at the entry point, 1.4 mm at the implant tip and 3.5° in angle compared with the plan ^[2]. A more recent meta-analysis compares the techniques ^[3]:

Full guidance is therefore more accurate than partial guidance, a finding also seen in another meta-analysis ^[4]. But more accurate does not automatically mean superior clinical results in the long term: an umbrella review of systematic reviews found no difference in implant survival or bone loss between guided and freehand surgery, and suggested that guidance may mainly reduce surgical risk in complex treatments ^[5]. The authors recommend keeping a safety margin of at least 2 mm from sensitive structures ^{[2, 3]}.

How is the implant placed?

Placement is carried out under local anaesthetic, in the practice’s operating room in Levallois-Perret. Depending on the case, the gum is opened to see the bone, or the implant is placed through a small opening when the guide allows it; it is inserted in the position decided during planning. It is then either covered by the gum during healing, or left flush with a small healing component that shapes the gum. The practical arrangements, the course of treatment and aftercare instructions are explained at the practice, according to your situation.

Healing and loading

Loading is when the implant receives a tooth. It can be immediate (shortly after placement), early, or conventional (once osseointegration is achieved). A Cochrane review of 26 randomised trials found no clinically important difference in failure between these options, with very low certainty of evidence ^[6]. The choice depends on how stable the implant is at placement, bone quality and whether a graft was needed.

Once osseointegration is achieved, an impression is taken and the final crown, screwed or cemented onto an abutment, is fitted. Its design matters for what follows: a crown that leaves room for interdental brushes can be cleaned, whereas a crown that is too bulky at the neck retains plaque.

How long does an implant last?

A meta-analysis estimates ten-year survival at 96.4%, and 93.2% in a more conservative sensitivity analysis ^[7]. These figures are averages: your own risk depends on factors that can partly be changed.

The main long-term threat is not mechanical but infectious: peri-implantitis, inflammation of the tissues around the implant with loss of supporting bone. It is prevented by appropriate daily cleaning and by maintenance visits whose frequency depends on your risk. The article Gum care around implants details these habits.

Contraindications and risk factors

• Smoking. A systematic review of 44 studies links smoking with a higher risk of implant failure and an average of 0.64 mm of additional bone loss; it is not an absolute contraindication, but support to stop smoking should be part of the treatment plan ^[8].
• Poorly controlled diabetes. Poorly controlled diabetes is associated with more peri-implantitis and, in the long term, more implant loss; when diabetes is well controlled, results are comparable to those of people without diabetes ^[9].
• History of periodontitis. It is associated with more peri-implantitis and slightly lower survival ^[10]. A review prepared for the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases lists a history of periodontitis, poor plaque control and lack of regular maintenance among the risk factors for peri-implantitis supported by strong evidence ^[11].
• Situations assessed case by case: some bone medications (antiresorptives), head and neck radiotherapy, or an unstable general condition. These are discussed with your doctor.

Frequently asked questions